Abstract: An agile steering control arrangement is provided for a spacecraft having a skewed scissor pair control moment gyro (SSP CMG) attitude control arrangement gimbaled with respect to the spacecraft body. The control arrangement includes a steering control process which converts arbitrary spacecraft boresight commands into spin torque and gimbal rate commands for a pair of spinning CMG. The steering control process generates suitable CMG torque commands based on requiring that the boresight nominally follow an arbitrary boresight trajectory described by required angular accelerations for the boresight together with one of various requirements on yaw motion. In this manner, a SSP CMG actuated spacecraft can be steered having tight boresight control while allowing a certain amount of error in yaw about the desired boresight. If spin motor capacities are exceed, new gimbal rates are determined based on saturation wheel spin torque.

Abstract: A method of attitude measurement for an artificial satellite (100) utilizes one or more star trackers (12) together with an earth sensor (30). Periodic updates of satellite orbital information, either propagated onboard or from a ground station are combined with earth and star position coordinate data to provide a continuous and accurate measurement of the spacecraft body 3-axis attitude. The method can be used for ground-based attitude determination or onboard closed loop control systems.